An expanding monoculture of the mangrove Avicennia marina var. resinifera growing at its southern limit in New Zealand was modelled using a Leslie matrix technique which assumed exponential population growth.

The predictions from the model were partially verified from sequential aerial photographs of the population. The results add to a growing body of practical experience in the application of matrix techniques to plant demography.

Modelling indicates that survivorship of the young tree size class is the main determinant of the population growth rate; annual seed production is relatively unimportant.

Avicennia trees produce relatively few large viviparous propagules, each of which has a high probability of establishment. Seedlings are retained in a ‘seedling bank’ for several years.

The λ value of 1.2228 reflects the colonizing ability of the species, and is compared with published values for other species.